The overall objective of the proposed research is to gain a better understanding of the mechanisms responsible for regulating normal synthesis of chondroitin sulfate proteoglycan as well as those responsible for changes in synthesis during cartilage development and in certain disease states. Since chondroitin sulfate is the end product of a complex biosynthetic pathway, a number of sites exist at which its metabolism may be regulated in the intact cell. Therefore, the various steps of biosynthesis of chondroitin sulfate proteoglycan which may serve as a locus of control will be separately assessed. 1) In cell-free studies, the composition, structure and organization of the biosynthetic components (glycosyltransferases and sulfotransferases), as well as the interactions of these purified components in selective reassembled systems, will be examined. 2) Studies on the structure and sequence of chondroitin sulfate core protein obtained following deglycosylation of proteoglycan or in vitro translation, will be carried out. 3) In a cell culture system, which has been well characterized, the production of chondroitin sulfate proteoglycan will be artificially perturbed, in order to elucidate the consequence to cell behavior and tissue organization of the altered synthesis of this specific product. 4) Similarly, the specific defect responsible for altered chondroitin sulfate proteoglycan synthesis in a mutant mouse system, will be localized and subsequently utilized as a model system for studies which eventually will extend to certain human chondrodystrophies.